Control of Common Groundsel in Florida Container Nurseries 1

Archival copy: for current recommendations see http://edis.ifas.ufl.edu or your local extension office.

ENH980

Alejandro Bolques, Jeffrey G. Norcini, James Aldrich, Courtney E. Gist2 Description

Common groundsel (Senecio vulgaris L.) is a weed that needs to be monitored year-round in container nurseries since these conditions are ideal for common groundsel. Seed can germinate only a few days after they land on the container medium surface (Figure 1).

If left uncontrolled, plants will grow up to 18 inches tall with multiple flowering stalks (Figure 2). Flowers are tubular in shape and seeds are tipped with a tuft of silky white hairs (Figure 3). Under Florida container nursery conditions, the whole life Figure 1. Common groundsel seedling. Credits: James cycle — from seed germination to flowering and seed Altland, Oregon State University, North Willamette set — can occur in as little as 6 weeks. Research and Extension Center, Aurora.

Common groundsel has only been officially groundsel as its ocurrence is probably more reported in Escambia, Gadsden, and Lake Counties, widespread. but anyone in Florida producing containerized ornamentals should be on the lookout for common

1. This document is ENH980, one of a series of the Environmental Horticulture Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date September 2004. Visit the EDIS Web Site at http://edis.ifas.ufl.edu. 2. Alejandro Bolques, Horticulture Extension Agent, Florida A&M University College of Engineering Sciences, Technology and Agriculture, Cooperative Extension and Outreach Programs, Quincy, Florida 32351; Jeffrey G. Norcini, Associate Professor, native wildflower specialist, and James H. Aldrich, Senior Biological Scientist, North Florida Research & Education Center, Quincy, FL 32351; Courtney E. Gist, Extension Intern, Gadsden County Cooperative Extension Service. The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication does not signify our approval to the exclusion of other products of suitable composition. All chemicals should be used in accordance with directions on the manufacturer's label. Use pesticides safely. Read and follow directions on the manufacturer's label.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry Arrington, Dean Archival copy: for current recommendations see http://edis.ifas.ufl.edu or your local extension office.

Control of Common Groundsel in Florida Container Nurseries 2

measures are not taken to control it. We describe below some methods to control this weed.

Sanitation. Check for common groundsel during your scouting routine for insects and diseases. Eliminate infestations on bed perimeters, in aisles, and on the perimeter of the nursery. Since common groundsel can be biennial, use a postemergence herbicide that is nonselective and translocated throughout the plant to ensure that the roots are killed. If the roots are not killed, the shoots will resprout. In general, use an herbicide that contains either glyphosate (for example, Roundup¨ ) or glufosinate (Finale¨) as the only active ingredient since some products contain other active ingredients not suitable for use in container nurseries. Exceptions to this rule are specially formulated products like QuikPROª Herbicide (glyphosate + diquat) that are labeled for control of groundsel. For long-term control, tank mix a labeled preemergence herbicide that is compatible with the postmergence herbicide. Some preemergence herbicides labeled for control of groundsel are listed in Table 1; however, check the postemergence and preemergence herbicide labels to determine if they can be tank mixed and used in your

Figure 2. Typical appearance of mature common situation. Reapply a preemergence herbicide as groundsel. Credits: Susan Aldrich-Markham, Oregon State needed according to label guidelines. University Extension Service, McMinnville. Do not mow or use a string trimmer to eliminate plants that have flowered as you probably will spread more seed. When crops are repotted or being brought into the nursery for the first time, carefully check for and remove common groundsel plants and seedlings. If the common groundsel in a pot has seedheads, repot the plant in fresh medium that is free of weed seeds. Apply a preemergence herbicide and irrigate the plants to activate the herbicide and form a protective barrier on the medium surface.

Preemergence Herbicides for Container Crops. An integrated approach of sanitation plus the Figure 3. Closeup of common groundsel flowers and seedhead. Credits: Susan Aldrich-Markham, Oregon State use of preemergence herbicides should prevent any University Extension Service, McMinnville. significant infestations of common groundsel. There are several preemergence herbicides labeled for Control control of common groundsel or groundsel species in general. Since seeds are easily spread by wind and each plant can produce about a million seeds, common In 2002, we evaluated several of these herbicides groundsel can spread quickly throughout a nursery if under container nursery conditions (Table 1) (Bolques et. al, 2003). One day prior to herbicide Archival copy: for current recommendations see http://edis.ifas.ufl.edu or your local extension office.

Control of Common Groundsel in Florida Container Nurseries 3 application in late May, 50 common groundsel seeds Postmergence Herbicides for Container Crops. were spread evenly over individual 1-gallon Common groundsel that has infested containers containers filled with 80:10:10, pine bark:peat:sand probably will have to be removed manually. Goal¨ (by vol.) amended with 13-6-6 sludge (Graco 2XL is labeled for postemergence control of common Fertilizer, Cairo, GA). Seeds were derived from groundsel (< 4 inches tall) for only a very limited plants found at a Gadsden County container nursery. number of container-grown, coniferous species. We Four single-pot replications per herbicide treatment are not aware of any other postemergence herbicide were randomly arranged on a full sun bed. Number labeled for control of common groundsel in of common groundsel in each pot were counted 2, 4, container-grown ornamentals. and 12 weeks after the herbicdes were applied. Nonherbicide-treated pots served as controls. Conclusion. To prevent common groundsel infestation, use good exclusion and sanitation Galleryª, Princep¨, and Snapshotª TG practices augmented with preemergence herbicides. provided the best control of common groundsel throughout the study. By 4 weeks after treatment, Literature Cited 100% control was observed in all pots treated with Bolques, A., J.G. Norcini, and J.H. Aldrich. these herbicides; 100% control was also observed at 2003. Preemergent control of common groundsel 12 weeks (Table 1). Moreover, there were never (Senecio vulgaris). Proc. Southern Nursery Assoc. more than two seedlings in any pot treated with these Res. Conf. 48:333-336. herbicides, and none of them flowered. Ronstar¨ 2G clearly provided the least control (62% to 76%). Gallitano, L.B. and W.A. Skroch. 1993. Most other herbicides provided at least 90% control Herbicide efficacy for production of container by 4 weeks after application and maintained that level ornamentals. Weed Tech. 7:103-111. of control another 8 weeks. The only exception was Ronstar¨ 50WP which provided 80% control at 4 Holliday, R.J. and P.D. Putwain. 1977. Evolution weeks and 84% control at 12 weeks. Gallitano and of resistance to simazine in Senecio vulgaris L. Weed Skroch (1993) reported 100% groundsel control with Res. 17:291-296. Galleryª nearly 29 weeks after application but slightly better control of groundsel than we observed Holliday, R.J. and P.D. Putwain. 1980. Evolution with Rout¨ and OH-II¨, and even better control with of herbicide resistance in Senecio vulgaris L: Ronstar¨ 2G. In their experiment, Ronstar¨ 2G Variation in susceptibility to simazine between and provided 100% control at 29 weeks. within populations. J. Appl. Ecol. 17:770-791.

Despite substantial reductions in number of Kadereit, J.W. and D. Briggs. 1985. Speed of groundsel in our herbicide-treated pots, many of the development of radiate and non-radiate plants of groundsel in those pots flowered. Moreover, we Senecio vulgaris L. from habitats subject to different observed that common groundsel seed could mature degrees of weeding pressure. New Phytol. soon after flowering, spread easily by air currents, and 99:155-169. germinate within a few days after settling in pots. Theaker, A.J. and D. Briggs. 1993. Relatively rapid development (germination to mature Genecological studies of groundsel (Senecio vulgaris seed) under container production conditions seems to L.). IV. Rate of development in plants from different be characteristic of at least some populations of habitat types. New Phytol. 123:185-194. common groundsel (Kadereit and Briggs, 1985; Theaker and Briggs, 1993). Thus herbicides providing any less than 100% preemergence control might result in a common groundsel infestation unless vigorous roguing of escapes is practiced. Archival copy: for current recommendations see http://edis.ifas.ufl.edu or your local extension office.

Control of Common Groundsel in Florida Container Nurseries 4

Table 1. Preemergent control of common groundsel under typical container nursery conditions.

Herbicide

Trade name Active ingredient Rate (lb ai/A) % Control 12 WATz

Galleryª 75DF isoxaben 1.0 100by

Goal¨ 2XL oxyfluorfen 0.5 90ab

OH II¨ pendimethalin + oxyfluorfen 1.0 + 2.0 91ab

Princep¨ L simazine 4.0z 100b

Regal O-O Herbicide¨ oxadiazon + oxyfluorfen 1.0 + 2.0 91ab

Ronstar¨ 2G oxadiazon 4.0 76a

Ronstar¨ 50WP oxadiazon 4.0 84ab

Rout¨ oryzalin + oxyfluorfen 1.0 + 2.0 90ab Snapshotª TG isoxaben + trifluralin 1.0 + 4.0 100b

z WAT = Weeks after treatment; compared to nontreated pots. y % control means with the same letter are not significantly different. zA high rate of Princep¨ was used to determine if the common groundsel from Gadsden County was resistant to simazine as has been reported for some other populations (Holliday and Putwain, 1977; Holliday and Putwain, 1980).